Vibration damper



April 21, 1953 H. w. WELSH VIBRATION DAMPER Fild Dec. 50, 1949 JNVENTOR. HARVEY w. WELSH BYZ;

ATTCIRNEY Patented Apr. 21, 1953 VIBRATION DAMPER Harvey W. Welsh, Wyckoff, N. J., assignor to Curtiss-Wright Corporation, a corporation of Delaware Application December 30, 1949, Serial No. 135,913

(Cl. I4-574) 8 Claims.

This invention relates to torsional vibration damping means and is particularly directed to torsional vibration damping means utilizing a fluid containing a suspension of finely divided ferromagnetic particles.

The operating characteristics of a torsional vibration damper embodying the present invention are somewhat similar to those of a conventional viscous torsional Vibration damper except that during normal operation the eifectiveness of the damper of the present invention is substantially independent of temperature as compared to the effectiveness of said conventional viscous torsional damper. A conventional viscous torsional damper is a simple structure for damping torsional vibrations of a shaft. Such a damper generally comprises a casing rotatable with a shaft Whose torsional vibrations are to be damped, said casing containing a high viscosity liquid Within Which a ring is floatingly immersed in clearance relation with the walls of said casing. In such a damper the liquid must be sufficiently viscous in order that the required damping forces can be obtained with reasonable clearance between the floating ring and its casing. However, even With the heavy silicone liquids now available the Viscosity of the liquid decreases substantially with increase in temperature. Accordingly the damping eiect of prior art viscous torsional dampers decreases substantially with increase in temperature.

A so-called magnetic fluid" has recently been developed for clutches and is described in an article entitled The Magnetic Fluid Clutch published in the Transactions of the American Institute of Electrical Engineers, pages 1308 to 1315, volume 67, 1948. This magnetic uid comprises a liquid, such as oil, Within which nely divided ferromagnetic particles, such as iron particles, are suspended. When such a fluid is placed in a magnetic field it seemingly solidifles to an extent dependent on the strength of the magnetic field. Accordingly, if the viscosity of the magnetic fluid in its unmagnetized condition is negligible, then its viscosity when magnetized is substantially independent of its temperature. An object of the present invention comprises the provision of a torsional vibration damper utilizing such a magnetic fluid. More specifically, the torsional damper of the present invention comprises a casing drivably connected to the shaft whose torsional vibrations are to be damped, said casing containing a magnetic fluid and a ring, having a plurality of circumferentially spaced magnets, is oatingly immersed in said uid.

A further object of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

Figure 1 is a schematic perspective view partly in section of a torsional vibration damper embodying the invention;

Figure 2 is a developed section taken along lines 2 2 of Figure l;

Figure 3 is a sectional view taken along lines 3-3 of Figure 1; and

Figure 4 is a transverse sectional view of a modified construction.

Referring now to Figures l to 3 of the drawing, a shaft I0 whose torsional vibrations are to be damped is provided with an annular housing or casing I2 concentric with and connected to said shaft by means of a web I4. A floating ring I6 is disposed within the casing I2. As schematically illustrated, the shaft I0 and casing I2 have an integral one-piece construction. In any practical embodiment, however, the casing I2 Would have a multi-part construction in order to permit the ring I6 to be disposed therein and said casing Would be rigidly secured to and about the shaft Il) for rotation with said shaft.

The casing I2 contains a magnetic uid I8 such as described in the aforementioned article. This fluid comprises a liquid of low viscosity, preferably a light oil, within Which finely divided ferromagnetic particles, such as iron particles, are suspended. This liquid is so chosen that its viscosity is negligible compared to the viscosity of the magnetic uid I 8 in its magnetized condition. As a result, during normal damper operation the viscosity of the fluid I8 When magnetized is substantially independent of temperature as compared to the viscosity of the liquid of a conventional viscous damper having a viscosity comparable with the viscosity of the uid I8 in its magnetized condition.

The Width and radial dimensions of the ring I6 are less than the corresponding dimensions of the interior of the casing I2. The ring I6 and the magnetic fluid I8 ll the casing I2 so that the ring I6 is floatingly immersed in the magnetic fluid I8 Within the casing I2 in clearance relation relative to the interior Walls of said casing. The ring I6 is made of suitable material 20 of relatively loW magnetic permeability, as for example bronze, copper, etc. Imbedded Within the low permeability material -of the ring I6 are a plurality of circumferentially spaced and parallel bar-type permanent magnets 22 whereby the magneticV fluid kI8 is subjected to the magnetic field of said magnets. Each of the permanent magnets 22 extends from one axial end of the ring I6 to its other axial end, the north pole of any one magnet and the south pole of the two adjacent magnets being disposed at the same end of the ring. With this arrangement. the poles of the magnets 22 alternate in polarity around each end of the ring I6.

The magnetic field of the permanent magnets 22 makes the magnetic fluid I8 behave as a very viscous liquid whereby, because of said viscosity, the ring I6 is effective to dampen torsional vibrations of the shaft IU. Since the viscosity of the magnetic fluid I8 within the casing I2 is substantially independent of temperature, the damping effect resulting from the viscosity of said fluid is substantially independent of vtemperature.

The casingA I2 is preferably metallic so that any relative motion between the casing I2 and the ring I6 with itsA magnets 22 will causeV eddy currents to be generated in the casing I2. Accordingly torsional vibrations of the shaft I result in the generation of. eddy currents in the casing I2 thereby further damping said vibrations. This iurther damping effect is a-lsosubstantially independent of changes in temperature. The magnitude of the eddy currents. generated in the casing I2 is increased by the alternate north andsouthpole arrangement of the magnets 22 around each end of the ring I6.

Like a conventional viscous type torsional damper, the damper ofthe present invention has va simpleconstruction which, because of the ab- .sence of relatively-moving engaging mechanical parts, is substantially trouble-free. As comvpared to. a conventional viscous torsional vibraztion damper, however,v the effectiveness of the `damper of the present invention is relatively un- .aileoted by changes in temperature.

The damper illustrated in Figures l to 3, is not `tuned to any frequency oftorsional vibration. If desired, however, ,the damper may be so tuned' in a manner schematically illustrated in Figure 4.

In Figure 4 a floating ring 30 and casing v32 have been substituted'jfor the floating ring I6 .and casing I2 of Figures 1 to 3. The casing 32 is concentric withY a shaft (not shown), whose :torsional vibrationsv are to be damped, a web ,3-3 connecting said shaftand casing. The floating ring 30l andcasing 32 are provided with radially overlapping and circumferentially spacedjprojections 34 and 36. respectively. In addition a 4spring 38 is disposed between each adjacentpair .of projections 34 andl 36 whereby the springs'38 .oppose relative rotation of the casing'30 andring 32. Preferably the construction of" Figure 41is otherwise like that of Figures l to 3, Accordingly the body of the ring30 is made of low permeability material and said ring is provided withl` a plurality of circumferentially spaced and parallel permanent magnets 4I)` imbedded in said low permeability material, said magnets preferably being disposed in a manner similar to that illus-v trated inFigures 1 and2. In addition, as in Figure 1the casing 32'is filled with amagneticfiuid 42 whereby the magnets 40, make said fluidquite viscous.

With thisV construction of Figure 4, the springs 38' provide the floating ring30 withia natural frequency of vibration aboutits axis. This tuned construction greatly increases the effectiveness of the damper` fordamping torsional vibrations ofthe shaftl Vhavinga frequency equal'r tosaid.

natural frequency but said tuned construction makes the damper substantially ineffective at other frequencies. Obviously the tuned damper construction of Figure 4 could also be provided in a viscous damper employing a conventional nonmagnetic viscous liquid and a, non-magnetic floating ring in place of the magnetic fluid 42 and the ring 30.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications.

I claim as my invention:

l. Apparatus for damping torsional vibrations of a rotating shaft; said apparatus comprising a casing adapted to be driven by said shaft; a fluid Within said casing having the property that its viscosity increases in a magnetic field; a floating ring co-aXially disposed within said casing and immersed in said fiuid; and magnet means carried by said ring for subjecting said fluid to a magnetic field.

2. Apparatus for damping torsional vibrations of a rotating shaft; said apparatus comprising a metallic casing adapted to be driven by said shaft; a fluid within said casing having the property that its viscosity increases in a magnetic field; a iioating ring co-axially disposed within saidy casing and immersed in said fluid, said ring being of relatively low permeability compared to ferromagnetic material; and a plurality of permanent magnets carried by said ring for subjecting said fluid to the magnetic field of said magnets.

3. Apparatus for damping torsional vibrations of a rotating shaft; said apparatus comprising a casing adapted to be driven by said shaft; a fluid within said casing; said fluid comprising a liquid having finely divided particles of ferromagnetic material suspended therein; a floating ring coaxially disposed within said casing and immersed inl said fluid, said ring being of relatively low permeability compared-to saidparticles; and a plurality of permanent magnets carried by and circumferentially spaced about the axis of said ring for subjecting said fluid to the magnetic field of said magnets.

4. Apparatus for damping torsional vibrations of av rotating shaft; said apparatuscomprising a casing adapted to be driven by said shaft; ailuid within said casing; said-fluid comprising a liquid having finely divided particles of ferromagnetic material suspended therein; a floating ring coaxially disposedwithin said casingfand immersed in said fluid, said ring being of relatively low permeabilityv compared to said particles; and a plurality of permanent magnets carried by said ring anddisposed with their poles adjacent to the axially spaced ends of said ring with the magnetic poles at each endof said ring alternating in polarity around said end.

5; Apparatus for damping torsional vibrations of a rotating shaft; said apparatus comprising a metallic casing, adapted to be driven by said shaft; a fluidwithin said casing; said fluid comprising a liquid having finely divided particles of ferromagnetic material suspended therein; a floating ring co-axially disposed within said casing and immersed in said fluid, said ring being of relatively low permeability compared to said particles; and a plurality of circumferentially spaced bar-type permanent magnets each carried by and extending between the axially spaced ends of said ring with the magnetic poles of said magnets alternating in polarity around each end of said ring.

6. Apparatus for damping torsional vibrations of a rotating shaft; said apparatus comprising a casing to be driven by said shaft; a uid within said casing, said uid comprising a liquid having nely divided ferromagnetic particles suspended therein; a floating ring co-axially disposed within said casing and immersed in said uid; and magnet means carried by said ring for subjecting said fluid to a magnetic eld.

7. Apparatus for damping torsional vibrations of a rotating shaft; said apparatus comprising a casing to be driven by said shaft; a fluid within said casing, said fluid comprising a liquid having finely divided ferromagnetic particles suspended therein; a floating ring co-axially disposed within said casing and immersed in said fluid; and a plurality of permanent magnets carried by said ring and circumferentially spaced about the axis of said ring.

8. Apparatus for damping torsional Vibrations of a rotating shaft; said apparatus comprising a casing to be driven by said shaft; a fluid within said casing, said uid comprising a liquid having iinely divided ferromagnetic particles suspended therein; a floating ring co-aXially disposed Within said casing and immersed in said fluid; and a plurality of permanent magnets carried by said ring and circumferentially spaced about the axis of said ring with adjacent poles of adjacent magnets being of opposite polarity.

HARVEY W. WELSH.

References Cited in the le of this patent Publications: Raymond Engineering Laboratory, Inc., Sept. 17, 1948, Middletown, Conn., Operating Instructions for the Raymond Model 663 Fluid Magnetic Clutch.

Business Week, Dec. 18, 1948, pps. 48-50, Magnetized Iron-Oil Mixes in New Jobs."

General Electric Review, Sept. 1949, pps. 16-20, Permanent Magnets in Drag Devices and Torque Transmitting Couplings. 

